Antidiabetic agent

Abstract: An antidiabetic agent contains a spherical carbon (for example, an activated spherical carbon or a spherical carbonaceous adsorbent) as an active ingredient. The antidiabetic agent can be used for treating diabetes, preferably by oral administration and may be not painful to a patient conventional as opposed to injections of insulin. Unlike conventional antidiabetics, the antidiabetic agent may not induce hypoglycemia.

Description: BACKGROUND OF THE INVENTION (1) Field of the invention The present invention relates to an antidiabetic agent comprising a spherical carbon as an active ingredient. (2) Description of the Related Art Diabetes include primary diabetes which is mainly induced by hereditary causes and which is primarily caused by insulin deficiency, and secondary diabetes which is induced by acquired causes. A sympton common to the two types of diabetes is hyperglycemia, which causes complications such as neurophathy or retinopathy. The progress of these complications results in deuteropathies such as serous infection, sudden death, blindness, heart failure, cerebral infarction, myocardial infarction, and the like. Therefore, sufficient care must be given to chronic complications. Insulin and the orally administrable medicines such as sulfonylurea agents and biguanide agents are conventionally used as antidiabetics. However, insulin is completely ineffective when administered orally, and is nowadays clinically administered only by injection, which is painful to the patient. In addition to the pain, redness, swelling, induration, itching, etc. sometimes occur at the site of the injection. Further, repeated subcutaneous injections at the same site sometimes cause lipodystrophy such as atrophy or hypertrophy of subcutaneous fat. Hypoglycemia may also occur as a serious side effect of taking insulin. Specifically, sufficient care should be taken not to cause hypoglycemia due to over-injection. Careful administration is required for the patient in order to avoid condition which is liable to cause hypoglycemia. The above mentioned orally administrable antidiabetics cannot substitute completely for insulin insulin is still indispensable, because the orally administrable antidiabetics have no effect on diabetic conditions such as diabetic coma, juvenile diabetes, diabetes with ketoacidosis and serious infection. Medicines of the sulfonylurea agent group include tolbutamide, chlorpropamide, acetohexamide, tolazamide, glibenclamide, etc., all of which sometimes cause serious and delayed hypoglycemia and, thus, must be carefully administered. Medicines of the biguanide agent group include buformin, metformin, etc., which sometimes cause serious lactic acidosis or hypoglycemia and, thus, must be carefully administered. SUMMARY OF THE INVENTION It is an object of the present invention to provide an antidiabetic agent comprising a spherical carbon comprising an activated carbon, as an active ingredient. It is another object of the present invention to provide a method of treating diabetes which avoids the problems caused by insulin injections and conventional antidiabetics. The present inventor thoroughly investigated an active ingredient different from insulin or conventional orally administrable antidiabetics such as sulfonylurea agents and biguanide agents. As a result, the present inventor has discovered that the serum glucose values of diabetic rats are decreased by orally administering a spherical carbon to the rats. The present invention is based on these findings. In order to achieve the objects of the present invention, there is provided an antidiabetic agent comprising a spherical carbon comprising an activated carbon, as an active ingredient. The present invention further provides a method of treating diabetes which avoids the problems caused by insulin injections and conventional antidiabetics. Accordingly, the invention relates to the use of substantially spherical carbon comprising an activated carbon, as an active ingredient for the preparation of a pharmaceutical composition for treatment of diabetes. In one preferred emdodiment, the substantially spherical carbon comprises an activated spherical carbon. In another preferred embodiment, the substantially spherical carbon comprises a spherical carbonaceous adsorbent. In one advantageous embodiment, the substantially spherical carbon has a particle diameter ranging from 0.05 to 2 mm. In another preferred embodiment, the spherical carbonaceous adsorbent further has a pore radius of less than 8 nm (80 angestroms) in a pore amount of 0.2 to 1.0 ml/g, a total amount of acidic groups (A) of 0.30 to 1.20 meq/g, a total amount of basic groups (B) of 0.20 to 0.70 meq/g, and a ratio of the total amount of acidic groups (A) / total amount of basic groups (B) of 0.40 to 2.5. In one advantageous embodiment, the pharmaceutical composition is in a dosage unit form. In one prefered embodiment, the dosage unit form is a capsule, a stick package or a divided package. DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS The spherical carbon used as an active ingredient in the present invention is not particularly limited as long as it comprises an activated carbon having a spherical shape that can be used for medical treatment. Although a medical activated carbon powder is generally useful as an antidote, it is liable to cause constipation as a side effect, particularly, when the carbon powder is used repeatedly. This is critical problem because constipation at the time of illness is dangerous. The spherical carbon used in the present invention has a particle diameter ranging from 0.05 to 2 mm. When the diameter is less than 0.05 mm, side effects such as constipation and the like are not sufficiently eliminated. On the other hand, when the diameter is over 2 mm, oral administration of the spherical carbon becomes difficult, and the desired pharmacological effect does not appear quickly. The shape of the spherical carbon is an important factor for obtaining satisfactory medical effects of the present invention, and it is necessary that the spherical carbon has a substantially spherical shape. Any raw materials for activated carbon may be used for producing the spherical carbon in the present invention. Although examples of such raw materials include sawdust, coals, coconut-shells, petroleum pitches, coal pitches, and synthetic organic high polymers, petroleum hydrocarbons are preferred. In the present invention, it is preferred to use an activated spherical carbon and/or a spherical carbonaceous adsorbent as the spherical carbon. Particles of an activated spherical carbon that can be used in the present invention have a diameter of 0.05 to 2 mm. A fundamental method of producing the activated spherical carbon according to the present invention comprises forming a raw material into fine spherical particles, carbonizing the spherical particles, and then activating the carbonized particles. Various activation methods can be carried out, for example, using steam, chemicals , air, or carbon dioxide. The activated spherical carbon particles can be produced, for example, by the following three methods : A first method comprises forming a raw material powder into fine spherical particles using a binder such as pitch, carbonizing the particles by baking them in an inert atmosphere at 600 to 1000°C, and then activating the carbonized particles in an atmosphere of steam at 850 to 1000°C. A second method comprises forming melted pitch into fine spherical particles, oxidizing the particles in an atmosphere containing oxygen to render them infusible, and then carbonizing and activating the infusible particles under the same conditions as those in the first method, as disclosed, for example, in Japanese Patent Publication n° 51-76 (see US Patent n° 3,917,806). A third method comprises melt-extruding pitch to form a string-like pitch, breaking the string-like pitch, casting the broken product into hot water to obtain spherical particles, oxidizing the particules in an atmosphere containing oxygen to render the particles infusible, and then carbonizing and activating the infusible particles under the same conditions as those in the first method, as disclosed, for example, in Japanese patent Publication n° 59-10930 (see US Patent n° 4,420,443). The spherical carbonaceous adsorbent used in the present invention preferably comprises activated carbon particles having a diameter of 0.05 to 2 mm, a pore radius of not more than 8 nm (80 angestroms) in a pore amount of 0.2 to 1.0 ml/g, a total amount of acidic groups (A) of 0.30 to 1.20 meq/g, a total amount of basic groups (B) of 0.20 to 0.70 meq/g, and a ratio of the total amount of acidic groups (A) / total amount of basic groups (B) of 0.40 to 2.5. An example of these spherical carbonaceous adsorbents is disclosed in Japanese Patent Publication n° 62-11611 (see the specification of US Patent n° 4,681,764). The spherical carbonaceous adsorbent used in the present invention can be produced by further oxidizing and reducing, at a high temperature, activated spherical carbon particles having a diameter of 0.05 to 2 mm and a pore radius of not more than 80 angstroms in a pore amount of 0.2 to 1.0 ml/g. Oxidation and reduction at a high temperature are preferably effected so that the total amount of acidic groups (A) and the total amount of basic groups (B) of the spherical carbonaceous adsorbent obtained are adjusted within the ranges of 0.30 to 1.20 meq/g and 0.20 to 0.70 meq/g, respectively, and the ratio of the total amount of acidic groups (A) / total amount of basic groups (B) is adjusted within the range of 0.40 to 2.5. A series of the heat treatments on the activated spherical carbon confers on the spherical carbonaceous adsorbent a balance between the adsorbency to the acidic and basic substance as well as an adsorbency to the amphoteric substances. Usually, the activated spherical carbon has rather unbalanced functional groups between acidic groups and basic groups. Between the activated spherical carbon and the spherical carbonaceous adsorbent, there is a difference in the balance between acidic groups and basic groups on the internal surface of pores. The total amount of acidic groups (A) and the total amount of basic groups (B) are determined by the following usual methods: (a) Total amount of acidic groups (A) One gram of pulverized adsorbent specimen that passed through a Taylor standard sieve of 200 mesh is added to 50 ml of 0.05 N aqueous NaOH solution, followed by shaking for 48 hours. The resultant mixture is filtered to remove the adsorbent, and the filtrate is neutralized by titration. The total amount of acidic groups (A) is determined by the amount of NaOH consumed by the titration and is expressed in units of meq/g of specimen. (b) Total amount of basic groups (B) One gram of pulverized adsorbent specimen that passed through a Taylor standard sieve of 200 mesh is added to 50 ml of 0.05 N aqueous HCl solution, followed by shaking for 24 hours. The resultant mixture is filtered to remove the specimen, and the filtrate is neutralized by titration. The total amount of basic groups (B) is determined by the amount of HCl consumed by the titration and is expressed in units of meq/g of specimen. High temperature oxidation is performed by heating the particles at a high temperature in an oxidizing atmosphere containing oxygen, which is formed by using pure oxygen, nitrogen oxides, or air as an oxygen source. High temperature reduction is performed by heating the particles at a high temperature in an atmosphere of a gas that is inert to carbon. The atmosphere of a gas that is inert to carbon is formed by using nitrogen, argon, helium, or a mixture thereof. Oxidative heating is preferably carried out at 300 to 700 °C, more preferably at 400 to 600°C, in an atmosphere preferably containing 0.5 to 25 % by volume of oxygen, more preferably 3 to 10% by volume of oxygen. Reduction is preferably carried out at 700 to 1100°C, more preferably 800 to 1000°C, in an atmosphere of nitrogen. The present inventor orally administered the above spherical carbonaceous adsorbent to diabetic rats that had been administered with streptozotocin. As a result, the inventor found the surprising phenomenon that serum glucose values of the rats decreased. It was thus found that a medicine containing as an active ingredient the spherical carbon is useful as an antidiabetic agent for diabetes. As a mattter of course, this medicine is useful for treating the chronic complications of diabetes, such as retinopathy or neuropathy, which are caused by hyperglycemia. In addition, importantly, when the antidiabetic agent of the present invention was administered to normal rats, no abnormality was induced, and hypoglycemia did not occur. The antidiabetic agent of the present invention can preferably be administered orally. The dosage depends on the subject (animal or human), the age of the subject, differences amoung subjects, the conditions of the disease, etc. For example, the oral dosage of the spherical carbon for human is generally within the range of 0.2 to 20 g per day. The dosage may be administered at one time or in 2 to 4 portions. The daily dosage may be adjusted appropriately according to symptoms. Thus, the spherical carbon can be administered as it is or in the form of a pharmaceutical composition as an antidiabetic agent. When the spherical carbon particles are used as they stand , it is most convenient to ingest a pharmaceutically acceptable aqueous slurry in which the particles are dispersed in drinking water. The spherical carbon particles may be administered as a medicine to patients in any desired form such as granules, tablets, sugar-coated tablets, capsules, stick, packages, divided packages, suspensions, or the like. When the particles are administered in the form of capsules, ordinary gelatin caspules or, if necessary, enteric capsules may be used. When the carbon particles are used in the form of granules, tablets, or sugar-coated tablets, the form must be disintegrated into the original fine spherical particles in the alimentary canal of a patient. Although the content of the spherical carbon in a pharmacutical composition may be varied according to symptoms and other factors, it is usually 1 to 100 % by weight, preferably 10 to 99 % by weight. A pharmaceutical composition for diabetes may comprise the spherical carbon as it is in a dosage unit form such as a capsule, a stick package, or a divided package. That is, the spherical carbon particles as it is may be enclosed in a caspule or a container such as a stick or a divided bag, and the adsorbent particles are administered in the form of capsules, stick packages, or divided packages to a patient suffering from diabetes. The antidiabetic agent of the present invention can be used for treating diabetes, preferably by oral administration. Therefore, unlike the injection of insulin, the antidiabetic agent of the present invention may not give a patient pain. Further the antidiabetic agent of the present invention may not induce hypoglycemia and, thus, does not have the problem of the conventional antidiabetics which are liable to induce hypoglycemia. Although the present invention will be more precisely explained below with reference to examples, the scope of the present invention is not limited to these examples. Production Example 1: Preparation of a spherical carbonaceous adsorbent An autoclave equipped with a stirrer was charged with 100 g of naphthalene and 300 g of pitch (H/C=0.55, flow point 220°C) having an anisotropic region that was not localized under a polarization microscope. The resultant mixture was mixed well at 180°C to form a solution. Into the resulting solution, 1200 g of 0.5 % aqueous polyvinyl alcohol solution was added. Then, the mixture was vigorously stirred at 140°C for 30 minutes and cooled to room temperature under stirring to form a dispersion of spherical-particles. After a large part of water was separated form the dispersion, the remaining spherical particles were treated with hexane in an extractor to remove the naphthalene contained therein by extraction and then dried by air flow. The thus-obtained particles were then heated to 300°C at a rate of 25°C/h by a flow of heated air in a fluidized bed system, and were further maintained for 2 hours at 300°C to obtain infusible oxygen-containing spherical particles. The particles were then heated to 900°C in steam and kept at 900°C for 2 hours in steam so as to carbonize and activate the particles to obtain porous activated spherical carbon. The activated spherical carbon had a diameter of 0.05 to 1.0 mm and a pore radius of not more than 8 nm (80 angstroms) in a pore amount of 0.755 ml/g, which as determined by a methanol adsorption method using an automatic adsorption measuring apparatus. The thus-obtained activated spherical carbon particles were heated to 600°C in an atmosphere containing 3 % by volume of oxygen, and were further heated at 600°C for 3 hours in the same atmosphere using a fluidized bed. Then, the particles were further heated to 950°C in an atmosphere of nitrogen and kept at 950°C for 30 minutes in the same atmosphere to obtain an intended spherical carbonaceous adsorbent (hereinafter referred to as "Sample 1"). The spherical carbonaceous adsorbent particles had a diameter of 0.05 to 1 mm, a pore radius of not more than 8 nm (80 angstroms) in a pore amount of 0.751 ml/g, which was determined by the methanol adsorption method using an automatic adsorption measuring apparatus, a total amount of acidic groups (A) of 0.542 meq/g, a total amount of basic groups (B) of 0.525 meq/g, and a ratio of the total amount of acid groups (A) / total amount of basic groups (B) of 1.03. In acute toxicity tests of the spherical carbonaceous adsorbent which was orally administered to male and female rats (Cpb: WU: Wistar Randon), no abnormality was observed even at the maximum dosage (5000 mg/kg for male and female rats) based on the Guidelines for Toxicity Studies of Drugs (Notification n° 118 of the Pharmaceutical Affairs Bureau, Ministry of Health and Welfare, Japanese Government, February 15, 1984). Example 1: Effect of antidiabetic agent on diabetic rats Sample 1 obtained in Production Example 1 was used as the spherical carbonaceous adsorbent functioning as an active ingredient of the antidiabetic agent. According to the ordinary method of preparing a diabetic model, streptozotocin [41 mg/kg (rat body weight)] was administered to the caudal veins of male JCL-SD rats (body weight ranging from 200 to 230 g) to prepare diabetic model rats. After 10 days had elapsed since streptozotocin was administered, blood was collected from the jugular vein of each rat in the morning, serum was separated, and the serum glucose value was measured. The rats were then divided into two groups (a control group and an administration group; 6 rats each) so that there was no deviation between the groups. The control group and the administration group were freely fed on rat feed (produced by Japan CLEA) and rat feed (produced by Japan CLEA) containing 5 % spherical carbonaceous adsorbent, respectively, for 6 weeks. After 4 and 6 weeks had passed, blood was collected from the jugular vein of each rat in the morning, serum was separated, and the serum glucose value was measured. The results are shown in Table 1. As seen from Table 1, although the serum glucose values of the rats in the control group increased, all serum glucose values of the rats in the administration group decreased. This decrease in the serum glucose value suggests that abnormal metabolism is corrected. At the start after an elapse of 4 weeks After an elapse of 6 weeks Serum glucose value (mg/dl) Body weight (g) Serum glucose value (mg/dl) Serum glucose valule (mg/dl) Control group 454 ± 47 297 ± 7 573 ± 81 558 ± 68 Administration group 468 ± 35 297 ± 12 341 ± 124 344 ± 142 Significant difference p < 0.01 P<0.01 Value: Mean ± Standard deviation (n = 6) Significant difference test: Non-pair t-test Example 2: Effect of antidiabetic agent on normal rats Sample 1 was used as the spherical carbonaceous adsorbent as in Example 1. Male JCL-SD rats were weighed and divided into two groups (a control group and an administration group; 8 rats each) so that there was no deviation in body weight between the groups. The control group and the administration group were freely fed on rat feed (produced by Japan CLEA) and rat feed (produced by Japan CLEA) containing 5% spherical carbonaceous adsorbent, respectively, for 4 weeks. After 4 weeks had passed, blood was collected from the jugular vein of each rat in the morning, and the serum glucose value was measured. The results are shown in Table 2. As seen from Table 2, the spherical carbonaceous adsorbent did not induce hypoglycemia in the normal rats. Serum glucose value (mg/dl) Control group 213 ± 8 Administration group 215 ± 11 Significant difference NS Value: mean ± Standard deviation (n = 8) Significant difference test: Non-pair t-test. Formulation Example 1: Capsule Two hundred milligrams of spherical carbonaceous adsorbent obtained in Production Example 1 were enclosed in a gelatin capsule to form a capsule. Formulation Example 2: Stick package Two grams of spherical carbonaceous adsorbent obtained in Production Example 1 were put into a stick made of a laminated film (constitution = glassine paper/polyethylene/aluminum foil/polyethylene/polyvinylidene chloride ; thickness = 74 ± 8 µm) and was heat-sealed to produce a stick package.

Claims: Use of substantially spherical carbon, comprising an activated carbon having a spherical shape, as an active ingredient for the preparation of a pharmaceutical composition for treatment of diabetes. Use according to claim 1, wherein the substantially spherical carbon comprises a spherical carbonaceous adsorbent. Use according to anyone of claims 1 to 2, wherein the substantially spherical carbon has a particle diameter ranging from 0.05 to 2 mm. Use according to anyone of claims 1 to 3, wherein the spherical carbonaceous adsorbent further has a pore radius of less than 8 nm (80 angstroms) in a pore amount of 0.2 to 1.0 ml/g, a total amount of acidic groups (A) of 0.30 to 1.20 meq/g, a total amount of basic groups (B) of 0.20 to 0.70 meq/g, and a ratio of the total amount of acidic groups (A) / total amount of basic groups (B) of 0.40 to 2.5. Use according to anyone of claims 1 to 4, wherein the pharmaceutical composition is in a dosage unit form. Use according to claim 5, wherein the dosage unit form is a capsule, a stick package or a divided package.

Inventors: ISE MICHIHITO, ISE, MICHIHITO
Applicants: KUREHA CHEMICAL IND CO LTD, KUREHA CHEMICAL INDUSTRY CO., LTD.
Application year: 1994
Main classification: A61K33
IPC codes: A61P3, A61K33